NamesNavstar 11
GPS I-11
Mission typeNavigation
OperatorU.S. Air Force
COSPAR ID1985-093A [1]
SATCAT no.16129
Mission duration5 years (planned)
8.5 years (achieved)
Spacecraft properties
Spacecraft typeGPS Block I
ManufacturerRockwell Space Systems[2]
Launch mass758 kg (1,671 lb) [2]
Dimensions5.3 meters of long
Power400 watts
Start of mission
Launch date9 October 1985, 02:53 UTC
RocketAtlas E / SGS-2
(Atlas-55E) [3]
Launch siteVandenberg, SLC-3W[3]
General Dynamics
Entered service8 November 1985
End of mission
Deactivated14 April 1994
Orbital parameters
Reference systemGeocentric orbit[1]
RegimeMedium Earth orbit
Perigee altitude19,829 km (12,321 mi)
Apogee altitude20,532 km (12,758 mi)
Period717.90 minutes
← USA-5 (Navstar 10)
USA-35 (Navstar 12) →

USA-10, also known as Navstar 11, GPS I-11 and GPS SVN-11, was an American navigation satellite launched in 1985 as part of the Global Positioning System development programme. It was the last of eleven Block I GPS satellites to be launched.[2]


Global Positioning System (GPS) was developed by the U.S. Department of Defense to provide all-weather round-the-clock navigation capabilities for military ground, sea, and air forces. Since its implementation, GPS has also become an integral asset in numerous civilian applications and industries around the globe, including recreational used (e.g., boating, aircraft, hiking), corporate vehicle fleet tracking, and surveying. GPS employs 24 spacecraft in 20,200 km circular orbits inclined at 55°. These vehicles are placed in 6 orbit planes with four operational satellites in each plane.[1]


The first eleven spacecraft (GPS Block 1) were used to demonstrate the feasibility of the GPS system. They were 3-axis stabilized, nadir pointing using reaction wheels. Dual solar arrays supplied over 400 watts. They had S-band communications for control and telemetry and Ultra high frequency (UHF) cross-link between spacecraft. They were manufactured by Rockwell Space Systems, were 5.3 meters across with solar panels deployed, and had a design life expectancy of 5 years. Unlike the later operational satellites, GPS Block 1 spacecraft were inclined at 63°.[1]


USA-10 was launched at 02:53 UTC on 9 October 1985, atop an Atlas E launch vehicle with an SGS-2 upper stage. The Atlas used had the serial number 55E, and was originally built as an Atlas E.[3] The launch took place from Space Launch Complex 3W at Vandenberg Air Force Base,[4] and placed USA-10 into a transfer orbit. The satellite raised itself into medium Earth orbit using a Star-27 apogee motor.[2]


By 8 November 1985, USA-10 had been raised to an orbit with a perigee of 19,829 km (12,321 mi), an apogee of 20,532 km (12,758 mi), a period of 717.90 minutes, and 63.40° of inclination to the equator.[5] The satellite had a design life of 5 years and a mass of 758 kg (1,671 lb).[2] It broadcast the PRN 03 signal in the GPS demonstration constellation, and was retired from service on 14 April 1994.


  1. ^ a b c d "Navstar 11 1985-093A". NASA. 14 May 2020. Retrieved 19 November 2020. Public Domain This article incorporates text from this source, which is in the public domain.
  2. ^ a b c d e Krebs, Gunter. "GPS (Navstar)". Gunter's Space Report. Retrieved 12 July 2012.
  3. ^ a b c McDowell, Jonathan. "Launch Log". Jonathan's Space Report. Retrieved 12 July 2012.
  4. ^ McDowell, Jonathan. "Launch List". Launch Vehicle Database. Jonathan's Space Report. Retrieved 12 July 2012.
  5. ^ McDowell, Jonathan. "Satellite Catalog". Jonathan's Space Report. Retrieved 12 July 2012.